The present invention relates to signal processing, and more particularly to a method for echo processing in level measurement or time of flight ranging systems.
Pulse-echo acoustic ranging systems, also known as time-of-flight ranging systems, are commonly used in level measurement applications. Pulse-echo acoustic ranging systems determine the distance to a reflector (i.e. reflective surface) by measuring how long after transmission of a burst of energy pulses the echoes or reflected pulses are received. Such systems typically use ultrasonic pulses or pulsed radar or microwave signals.
Pulse-echo acoustic ranging systems generally include a transducer and a signal processor. The transducer serves the dual role of transmitting the energy pulses and receiving the reflected energy pulses or echoes. The signal processor is for detecting and calculating the distance or range of the object based on the transmit times of the transmitted energy pulses and the reflected energy pulses or echoes.
Since the reflected energy pulses or echoes are converted into distance measurements, any errors in the echoes result in distance measurement errors which degrade the accuracy of the level measurements.
Accordingly, there remains a need to provide a system and techniques which improve the processing of the reflected energy pulses or echoes.
The present invention provides a method for improved echo processing, and comprises a method for generating a new noise level signal which is based on the original noise level and any changed or modified portions.
In a first aspect, the present invention provides a method for generating an echo profile in a time-of-flight ranging system, said method comprising the steps of: (a) transmitting a transmit burst of energy to a reflective surface; (b) receiving reflected pulses from said reflective surface, and converting said reflected pulses into an echo signal; (c) establishing an initial noise floor level; (d) identifying one or more portions of said echo signal above said initial noise floor level as having potential echoes; (e) modifying one or more segments in said initial noise floor level, and generating an adjusted noise floor level; (f) wherein said step of generating comprises applying a cubic spline procedure to said modified segments and said initial noise floor level; (g) identifying valid echoes in the portions of said echo signal above said adjusted noise floor level; and (h) generating an echo profile using said identified valid echoes.
In a further aspect, the present invention provides a method for generating a noise floor level for an echo profile in a time of flight ranging system, said method comprising the steps of: (a) establishing an initial noise floor level; (b) modifying one or more points in said initial noise floor level; (c) applying a cubic spline algorithm to said modified points and said initial noise floor level to generate a plurality noise floor data points; (d) sampling said noise floor data points; (e) forming an adjusted noise floor level from said sampled noise floor data points.
In yet another aspect, the present invention provides a method for generating an echo profile in a time-of-flight ranging system, said method comprising the steps of: (a) transmitting a transmit burst of energy to a reflective surface; (b) receiving reflected pulses from said reflective surface, and converting said reflected pulses into an echo signal; (c) establishing an initial noise floor level; (d) subtracting said initial noise floor level from said echo signal to identify one or more potential echoes; (e) modifying one or more segments in said initial noise floor level, and generating an adjusted noise floor level; (f) wherein said step of generating comprises applying a cubic spline procedure to said modified segments and said initial noise floor level; (g) subtracting said adjusted noise floor level from said echo signal to identify one or more valid echoes said echo signal; and (h) generating an echo profile using said identified valid echoes.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying drawings.